1. Field of the Invention
The present invention relates to an LSI package provided with an interface (I/F) module, an interposer and an I/F module which are used in the LSI package, a signal processing LSI mounted on the interposer so as to implement the LSI package, a monitoring circuit of the LSI package configured to monitor an electrical connection between the signal processing LSI and the I/F module.
2. Description of the Related Art
With improvements in performance of semiconductor active elements such as bipolar transistors and field-effect transistors, the remarkable developments of operation speed is attempted in large scale integrated circuits for signal processing (hereinafter described “signal processing LSI”). However, the operation speed on a board level, or a printed circuit board mounting the signal processing LSI, is still lower than the operation speed in the signal processing LSI, although the operation speed in the signal processing LSI is inherently high, and further, on a rack level packaging hierarchy implemented by the printed circuit boards, the operation speed becomes further lower. The above-mentioned operation speed problems are caused by increases in transmission loss, noise, and electromagnetic interference associated with the electrical interconnections, which increase more and more as the operation frequency becomes higher. Namely, it is inevitable that as the wiring length becomes long, the operating frequency decreases so as to ensure the signal quality. Therefore, such a tendency the packaging technology limits the operation speed of the system rather than the operation speed of the signal processing LSI, has become more and more significant recently in the electrically interconnected device.
Taking such problem in the electrically interconnected device into consideration, optically interconnected devices configured to establish communications between signal processing LSIs by optical interconnection are proposed. In the optical interconnection, since the frequency dependence of losses, the electromagnetic interference in the distribution lines and noise associated with ground potential fluctuation can be ignored in a frequency range from direct current to a high frequency band over 100 GHz, communication of Gbps can be easily realized. Such optically interconnected device establishing communications between signal processing LSIs by optical interconnection is disclosed, for instance, in NIKKEI ELECTRONICS, No. 810, pp 121-122, Dec. 3, 2001, in which an I/F module adapted for external connection of high-speed signals is directly mounted on an interposer, on which a signal processing LSI is mounted, is proposed.
In the above-mentioned earlier technology, it is difficult to mount an interposer on a board in an actual interposer mounting process, since the mounting of the interposer on the board is carried out in a condition where the interposer is mingled with the I/F module.
For instance, since the I/F module has an optical transmission line such as an optical fiber, etc, it is not possible to give heat treatment by putting the optical fiber into a solder reflow furnace of the interposer as it is. The problem is not limited to a case in which the optical transmission line is employed, since the same problem arises when an electrical transmission line such as a small coaxial cable is used for the transmission line.
Then, in NIKKEI ELECTRONICS, the optical transmission line is formed so that it can be detached from the I/F module by a detachable optical connector. However, in the detachable optical connector methodology, protectors for protecting optical semiconductor elements and optical connectors from mechanical damage and pollution are required. And, in addition, various architectures for lowering the process temperature so as to prevent thermal deformation of joints of the optical connector and for shortening the processing time are required. Because of these requirements, there was a problem being that the mounting condition of other parts which are supposed to be mounted on the same board does not meet with the mounting condition of the I/F module and that existing board assembly equipment are not able to be applied to as they are. Furthermore, the configuration becomes more and more complicated because pressure mechanism and holding mechanism of the optical connector must be provided in the detachable optical connector methodology, and the manufacturing cost drastically increases.